1. Field of the Invention
The present invention relates to apparatus for performing a machining operation on a workpiece and, more particularly, to a means for setting up the apparatus prior to performing a machining operation.
The invention has particular application to the setting up of a centreless grinding machine to be used for the machining of nuclear fuel pellets.
2. Present State of the Art
In a typical centreless grinding machine a cylindrical workpiece is supported on an inclined work rest which is located between the peripheral surfaces of a control (or regulating) wheel and a grinding wheel. During the grinding operation the grinding wheel forces the workpiece downward against the work rest and also against the control wheel. To guide the finished machined workpiece from the control and grinding wheels, au outlet guide is positioned adjacent to the control wheel.
It is essential that the peripheral surface of the control wheel is aligned accurately with the outlet guide so that the machined workpiece is directed from the wheels in a straight lines. Misalignment of the control wheel surface and the outlet guide would result in the production of defectively machined products. Normally, this setting up procedure is done manually by an operative manipulating a typical workpiece across the interface between the control wheel and the outlet guide Simultaneously, the operative causes relative movement between the control wheel and the outlet guide and senses when the two are in alignment.
In certain situations it is difficult to set up the machine prior to a machining operation because of the restricted access to the various parts of the machine. One such situation concerns the use of centreless grinding machines for grinding nuclear pellets to the required diameter. Since the handling and machining of nuclear fuel pellets constitutes a health hazards it is necessary for safety reasons to locate the grinding machine in a protective enclosure. Thin presents problems when carrying out the setting up procedure.
It is an object of this invention to provide a means for facilitating the setting up of an apparatus for machining a workpiece.
According to a first aspect of the invention there is provided apparatus for performing a machining operation on a workpiece, the apparatus comprising a control member having a first surface for locating a workpiece during a machining operation, an outlet guide having a second surface for guiding a workpiece away from the control member, the control member and the outlet guide being movable relative to one another to enable alignment of the first and second surfaces, an electrical circuit including an indicating means, and a setting component comprising an electrically conducting portion for use in aligning the first and second surfaces prior to machining a workpiece, wherein relative movement of the control member and the outlet guide enables the electrically conducting portion of the component to complete the electrical circuit and thereby activate the indicating means when the first and second surfaces are in alignment.
The electrical circuit preferably includes the second surface and relative movement of the control member and outlet guide enables the electrically conducting portion to contact the second surface whereby to complete the electrical circuit.
Preferably the apparatus is adapted to produce cylindrical workpieces by the machining operation, the setting component being in the form of a cylinder having substantially the same diameter as a workpiece to be machined.
The setting component preferably comprises an electrically insulating portion and an electrically conducting portion.
In a preferred embodiment the electrically insulating portion and the electrically conducting portion are each in the form of a semi-cylinder.
Alternatively, the setting component may be formed wholly from an electrically conducting material.
Preferably the control member comprises a rotatable control wheel, the said first surface thereof being adapted to impart a rotatable drive to a workpiece.
The apparatus may further comprise a grinding wheel arranged for rotation about an axis extending in parallel relationship to an axis of rotation of the control wheel, the grinding wheel having a peripheral surface formed with an abrasive material for effecting the machining operation on a workpiece.
A workpiece support preferably extends between the first surface of the control wheel and the peripheral surface of the grinding wheel, the setting component being so arranged that the electrically insulating portion thereof contacts the workpiece support.
Adjustment means may be provided for moving the control wheel in a direction perpendicular to the axis of rotation thereof whereby to obtain relative movement of the first and second surfaces.
Alternatively, adjustment means may be provided for moving the outlet guide whereby to obtain relative movement of the first and second surfaces.
Preferably the indicating means comprises a visual indicator.
The indicating means may comprise a current meter or may be adapted to provide an audible signal,
According to a second aspect of the invention there is provided a method of setting up an apparatus for performing a machining operation on a workpiece, the apparatus comprising a control member having a first surface for locating a workpiece during a machining operation, an outlet guide having a second surface for guiding a workpiece away from the control member, an electrical circuit including an indicating means, and a setting component having an electrically conducting portion for use in aligning the first and second surfaces prior to machining the workpiece, the method comprising placing the setting component in contact with the first surface, causing relative movement of the control member and the outlet guide so as to allow the electrical conducting portion of the setting component to contact the second surface and thereby complete the electrical circuit, thereby activating the indicating means.